Illumination and observation system for an ophthalmic microscope, ophthalmic microscope comprising such a system, and microscopying method

ABSTRACT

An illumination and observation system (1), in particular for an ophthalmic microscope, comprises a first observation pupil (4) and a second observation pupil (5) for the eyes of an observer such as an assistant. Further, the system comprises a coaxial illumination (6) in the first observation pupil (4) and a main illumination (7), the coaxial illumination (6) being adapted to generate a red reflex (13) in the observed eye in operation and the main illumination having a larger field of illumination than the coaxial illumination (6, 10, 11). To facilitate usage of the system (1) and/or the microscope (2) and to create a superior stereoscopic view using the red reflex (13), a control subsystem (21, 27) is provided which is adapted to automatically adjust an intensity of the main illumination (7) depending on a change in an intensity of the coaxial illumination (6).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is the U.S. national phase of International Application No. PCT/SG2016/000011 filed Aug. 23, 2016, which claims priority of European Application No. 15182105.5 filed Aug. 24, 2015, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to an illumination and observation system for a microscope, in particular a microscope for performing eye surgery, wherein the system comprises a first and second observation pupil for the eyes of an observer such as an assistant, a coaxial illumination in the first observation pupil, the coaxial illumination being adapted to generate a red reflex in the observed eye in operation.

The invention further relates to a microscope, in particular for eye surgery comprising such a system. Finally, the invention relates to a microscopying method by using a coaxial illumination to illuminate the object coaxially through a first observation pupil and by using a main illumination to illuminate the object with a larger field of illumination in the object plane than the coaxial illumination.

BACKGROUND OF THE INVENTION

Ophthalmic microscopes, i.e. microscopes that are used for eye surgery, comprise typically two different kinds of illumination. A first illumination serves to illuminate a rather large field of illumination in the observed object, i.e. the eye to be operated, in particular in the object plane. This illumination lightens the surroundings of the area, where the actual observation takes place. In the object plane, the field of illumination of this type of illumination has typically a diameter between 60 mm and 80 mm. This illumination is referred to in the following as a main illumination. In eye surgery, the main illumination is primarily used to visualize outer eye structures like the cornea.

A second type of illumination makes use of the characteristic of the eye's retina to provide a reddish-orange reflection of light called the red reflex. The red reflex offers much higher contrasts than the main illumination and is mainly used for cataract surgery. The red reflex is generated by an illumination, which is coaxial or at least closely coaxial, e.g. within +/−5°, to the axis of an observer's pupil which looks through the illumination and observation system onto the observed eye. A known system for generating a red reflex is, for example, described in EP 0 661 020 B1. The field of illumination of the coaxial illumination is usually much smaller than the diameter of the main illumination, e.g. by a factor 2 to 5.

Operating an illumination and observation system and a microscope comprising such a system is often difficult and its manufacturing is expensive. Further, the image quality of the known illumination and observation systems, although having made large progress in the past, still leaves room for improvement.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to provide an illumination observation system that is easy to operate, inexpensive in its design, and at the same time offers superior observation properties.

This object is achieved, according to the invention, for the illumination and observation system as initially mentioned by a main illumination in the second observation pupil having a larger field of illumination in the object plane than the coaxial illumination and a control subsystem which is adapted to automatically adjust an intensity of the main illumination depending on a change in an intensity of the coaxial illumination. With respect to the microscopying method for illuminating an observed object, this object is achieved in that the intensity of the main illumination is controlled to automatically follow the intensity of the coaxial illumination.

By having the main illumination in the second observation pupil, i.e. directing the main illumination such that it is directed through and thus overlaps with the second observation pupil, a red reflex can be generated in the second observation pupil.

Further, by coupling the main illumination to the coaxial illumination, several advantages may be realized. First, the operation of the illumination and observation system or the microscope is facilitated, as the main illumination is automatically adapted to any change of the coaxial illumination. If the coaxial illumination is adapted to produce a stronger red reflex, the main illumination also gets stronger and contrast is maintained. Second, by coupling the intensity of the main illumination to the intensity of the coaxial illumination, it is possible that an intensity of the red reflex in the second observation pupil, which in most cases is invariably generated also by the main illumination, follows the intensity of the red reflex generated by the coaxial illumination. Thus, it is possible to generate an improved stereoscopic red reflex using the main illumination in one and a coaxial illumination in another observation pupil. Finally, the inventive solution has the advantage that a stereoscopic red reflex can be maintained without the need to include another expensive coaxial illumination.

The intensity may be easily measured at the plane of observation in the observed eye, e.g. in the SI unit lux, either as the intensity reflected from the observed object or as the intensity incident on the observed eye. For the purposes of this invention, even a subjective impression of a typical observation without an objective measurement of the intensity may be sufficient.

The solution according to the invention may be further improved by the following features, which may be combined independently of one another.

In one embodiment, the controlled subsystem may be adapted to set a ratio of the intensity of the main illumination to the intensity of the coaxial illumination at a target ratio independent of a change in the intensity of the coaxial illumination.

A preferred target ratio is in a range of 0.2 to 5, particularly preferable in a range of 0.5 to 2, even more preferable in a range of 0.5 to 1.5 measured in lux. Preferably, the target ratio is selected such that the intensity of the red reflex in the first observation pupil is perceived to be identical or almost identical to the intensity of the red reflex in the second observation pupil.

The target ratio may be independent of the intensity of the main illumination and/or the coaxial illumination and e.g. be factory-preset. The target ratio according to another embodiment, may also vary linearly or non-linearly depending on the intensity of the main illumination and/or the coaxial illumination.

According to another embodiment, the illumination and observation system may be configured to provide a user-adjustable target ratio. For adjusting the target ratio, a manipulator subsystem including for example mechanical manipulators such as knobs and sliders and/or software-implemented manipulators such as virtual knobs or sliders on a computer screen, may be provided.

According to another embodiment, a memory subsystem may be provided, which is adapted to store the target ratio. In the memory subsystem, the target ratio may be stored adjustable. The memory subsystem can comprise mechanical parts such as a mechanical manipulator the position of which sets and stores the target ratio. The memory subsystem may also comprise electronic memory, such as a digital memory, for storing the target ratio in digital and/or analog form.

The manipulator subsystem may further be adapted to change the intensity of at least one of the main and the coaxial illumination, for example by usage of one of the above-mentioned manipulators.

The manipulator subsystem according to another embodiment may be adapted to interact with at least one of the control subsystem and the memory subsystem to change the target ratio upon a manual input from an observer.

In order to achieve a superior quality of the red reflex, it is desired that the main illumination overlaps at least 50% with the second observation pupil.

The intensity of the red reflex can be improved if the main illumination overlaps the optical axis of the second observation pupil.

An improvement of the red reflex may also result from a main illumination, which is coaxial within +/−5° to the optical axis of the second observation pupil.

According to another advantageous embodiment, the illumination and observation system may further comprise a third and a fourth observation pupil, each of which is provided with a coaxial illumination. The third and fourth observation pupil may, in particular, be adapted to be used by a second observer, in particular a surgeon, whereas the first and second observation pupil may in particular be dedicated to an assistant or student assisting the surgeon during operation.

The intensities of the coaxial illumination in the third and fourth observation pupil are preferably coupled to each other. For adjustment purposes, however, the illumination and observation system may be adapted to allow a decoupling of the intensities of the coaxial illumination of the third and fourth observation pupil. In the decoupled state, at least one of the intensity of the coaxial illumination in the third observation pupil and the intensity of the coaxial illumination in the fourth observation pupil may be changed independently of each other. A subsequent coupling of the intensity of the coaxial illumination of the third and fourth observation pupil may maintain the ratio of the intensities of the coaxial illumination of the third and fourth observation pupil as it has been adjusted during the decoupling. The adjustment may be realized by the manipulator subsystem and by providing a storage subsystem which is adapted to store a ratio of the intensity of the coaxial illumination in the third and fourth observation pupil, and by the control subsystem to control the coaxial illumination in the third and fourth observation system during operation to maintain this ratio.

The manipulator subsystem may be adapted to switch the illumination and observation system from a coupled state, in which the intensity of the main illumination is coupled to the intensity of the coaxial illumination in at least one of the first, third and fourth observation pupil, to a decoupled state, in which the intensity of the coaxial illumination in at least one of the first, third or fourth observation pupil is decoupled from the intensity of the main illumination. The switching from the coupled state to the decoupled state and the switching back from the decoupled to the coupled state may be performed upon manual input. In the decoupled state, the manipulator subsystem may be adapted to adjust the relative intensities of the main illumination in the second observation pupil and the coaxial illumination in at least one of the other observation pupils independent from one another.

In order to allow an individual adjustment of the main illumination on one hand and the coaxial illumination of at least one of the first, third and fourth observation pupil on the other hand, it is preferred that the main illumination and the coaxial illumination of at least one of the first, third or fourth observation pupil have separate light sources. The control subsystem may be adapted to control the energy input to the separate light sources individually, at least in the decoupled state. In the coupled state, the light source of the main illumination may be operatively coupled to at least one of the light sources for the coaxial illumination.

To provide a homogeneous red reflex in all observation pupils, it is preferred that the coaxial illumination overlaps at least one of the first, third and fourth observation pupil by at least 50% and/or covers the optical axis of the respective observation pupil. According to a particularly preferred embodiment, each of the coaxial illuminations and the main illumination overlaps at least 50% of the first, second, third and fourth observation pupil.

BRIEF DESCRIPTION OF THE DRAWING VIEWS

In the following, the invention is explained exemplarily with reference to the drawings. In the drawings, the same reference numerals are used for elements that correspond to each other. The various features in the drawings can be combined independently of each other as is laid out above.

In the drawings:

FIG. 1 shows a schematic representation of an illumination and observation system according to the invention;

FIG. 2 shows a schematic representation of the illumination and observation system according to FIG. 1 with additional components;

FIG. 3A shows a schematic representation of a red reflex resulting from an illumination and observation system as shown in FIG. 3B;

FIG. 3B shows a schematic representation of the illumination generating the red reflex of FIG. 3A;

FIG. 4A shows a schematic representation of a red reflex resulting from an illumination and observation system as shown in FIG. 4B;

FIG. 4B shows a schematic representation of the illumination generating the red reflex of FIG. 4A;

FIG. 5A shows a schematic representation of a red reflex resulting from an illumination as shown in FIG. 5B;

FIG. 5B shows a schematic representation of the illumination generating the red reflex of FIG. 5A;

FIG. 6 shows a schematic side view upon the illumination and observation system according to the invention as used in a microscope; and

FIG. 7 shows a schematic perspective view of the embodiment shown in FIG. 6 with additional elements.

DETAILED DESCRIPTION OF THE INVENTION

First, the design and function of an illumination and observation system 1 in a microscope 2 is explained with reference to FIG. 1. FIG. 1 shows a schematic plan view of a main objective lens 3 with a first observation pupil 4 and a second observation pupil 5. The first observation pupil 4 and the second observation pupil 5 are preferably for an assistant or a student assisting in e.g. eye surgery.

A coaxial illumination 6 is directed through the first observation pupil 4, whereas a main illumination 7 is directed through the second observation pupil 5. Preferably, there is no overlap of the main illumination with the first observation pupil 4 and/or there is no coaxial illumination in the second observation pupil 5.

The set up shown in FIG. 1 is particularly useful for microscopes 2 which are used in eye surgery, i.e. so-called ophthalmic microscopes. At the observed object, i.e. in the object plane, in such a case the eye to be operated upon, the main illumination 7 generates a field of illumination which has a larger diameter in the observation plane than the coaxial illumination 6. The field of illumination may be between 60 mm and 80 mm. The axis of the coaxial illumination 6 deviates only slightly from the optical axis of the first observation pupil 4, e.g. by less than +/−5°.

As can be seen in FIG. 1, the main illumination 7 is also arranged to be coaxial at least within +/−5° to the optical axis of the second observation pupil 5. Thus, both the main illumination 7 and the coaxial illumination 6 are able to generate a red reflex during eye surgery.

To provide a homogeneous red reflex, it is preferred that the main illumination 7 and the coaxial illumination 6 overlap the respective observation pupil 5, 4 at least by 50% with regard to its area.

To provide a good stereoscopic effect in the red reflex, the intensity of the main illumination should be kept at a certain target ratio to the intensity of the coaxial illumination. A preferred intensity target ratio is in a range of 0.2 to 5, particularly preferable in a range of 0.5 to 2, even more preferable in a range of 0.5 to 1.5 measured in lux. Thereby, the intensity of the red reflex in the first observation pupil is perceived to be identical or almost identical to the intensity of the red reflex in the second observation pupil.

The target ratio of the intensity of the main illumination to the coaxial illumination is maintained by the illumination and observation system 1 independently of the intensity of the coaxial illumination 6. In particular, the intensity of the main illumination 7 may be coupled to the intensity of the coaxial illumination 6: if the intensity of the coaxial illumination 6 changes, e.g. by manual operation of a user, the intensity of the main illumination 7 follows to maintain the same intensity ratio of the red reflex in both observation pupils 4, 5.

The observation illumination system shown in FIG. 1 may be expanded to comprise a third observation pupil 8 and a fourth observation pupil 9, each of which is provided with a respective coaxial illumination 10, 11, which may substantially correspond to the coaxial illumination of the first observation pupil 4.

The third and fourth observation pupil 8, 9 may be specifically used by a surgeon. The coaxial illuminations 10, 11 are preferably identical, comprising identical and/or identically arranged optical elements, to produce an identical red reflex in the observed eye for both observation pupils 8, 9. Preferably, there is no main illumination overlap in the third and/or fourth observation pupil 8, 9.

The intensity of the coaxial illumination 6 for the first observation pupil 4 may be coupled to the intensity of at least one of the coaxial illumination 10 in the third observation pupil 8 and the coaxial illumination 11 in the fourth observation pupil 9. If the surgeon adjusts the intensity of the coaxial illumination 10, 11, the intensity of the coaxial illumination 6 in the first observation pupil 4 will automatically follow. Due to the coupling of the main illumination 7 in the second observation pupil 5 to the intensity of the coaxial illumination 6 in the first observation pupil 4, the intensity of the main illumination 7 will thus automatically follow any adjustment of the coaxial illumination 10, 11 in the third and fourth observation pupil 8, 9.

The coaxial illumination 10 overlaps the third observation pupil 8 by more than 50% and the coaxial illumination 11 overlaps the fourth observation pupil 9 by more than 50%. Moreover, a red reflex is generated in all four observation pupils 4, 5, 8, 9. According to the invention, due to a coaxial alignment of the main illumination, a strong red reflex can be generated in the second observation pupil 5 without the need to install an expensive coaxial illumination. Rather, the main illumination 7 is aligned with the optical axis 12 of the second observation pupil 5 and its intensity is maintained at the target ratio to the intensity of the coaxial illumination in the first observation pupil 4.

Using an overlap of more than 50% increases the homogeneity of the red reflex. This is schematically shown in FIGS. 3A,B, 4A,B and 5A,B. In these figures, a coaxial illumination 6, 10, 11 is shown to overlap with one of the observation pupils 4, 8, 9. The overlap leads to a red reflex which has a perceptible inhomogeneous intensity distribution in the respective observation pupils 4, 8, 9 as seen by the respective observer. Increasing the overlap reduces the inhomogeneity shown in FIGS. 3A, 4A and 5A.

FIG. 6 shows a schematic side view of parts of the illumination and observation system 1 as used in the microscope 2. The illuminations 6, 7, 10, 11 are aligned with and directed through the respective observation pupil 4, 5, 8, 9 by using beam splitters 14, 15. A larger beam splitter 14 is used to deflect the main illumination 7 for the second observation pupil 5 and the coaxial illuminations 10, 11 for the third and fourth observation pupil 8, 9 respectively. A second, smaller beam splitter 15 is used to deflect the coaxial illumination 6 for the first observation pupil 4.

Each of the illuminations 6, 7, 10, 11 is preferably provided with a separate light source 16, which in particular may be an LED 17. As in the view of FIG. 6, the third and fourth observation pupil 8, 9 together with the respective coaxial illuminations 10, 11 are located right behind each other, only one light source 16 is shown for these two coaxial illuminations 10, 11.

Using the beam splitters 14, 15 results in a very good alignment, not only of the coaxial illuminations 6, 10, 11 with the optical axes 12 of the first, third and fourth observation pupil 4, 8, 9, but also of the main illumination 7 with the optical axis 12 of the second observation pupil 5.

Between the light sources 16 and the beam splitters 14, 15, optical elements such as lenses 18 for the coaxial illumination 6, 10, 11 and 19 for the main illumination 7 may be arranged. The optical elements 18, 19 may also comprise an aperture which may be adjustable.

In FIG. 7, the embodiment of FIG. 6 is shown in a schematic perspective view. From this, it can be seen that there is a single optical element 18 such as a lens associated with the three separate light sources 17 for the coaxial illuminations 6, 10, 11. The illumination and observation system 1 may have an identical design along the illumination paths 20 of the coaxial illuminations 6, 10, 11, so that the coaxial illuminations 6, 10, 11 in the first, third and observation pupil 4, 8, 9 have identical or at least almost identical properties.

The light sources 16 may be arranged geometrically in a pattern that corresponds to the pattern of the observation pupils 4, 8, 9 which are equipped with coaxial illumination 6, 10, 11.

The light sources 16 for generating the coaxial illumination 7, 10, 11 may be adapted to be controlled independently of each other or they may be coupled to each other. A control subsystem 21 is adapted to control the intensity of the light sources 16 for the coaxial illumination 6, 10, 11. The control subsystem 21 may be adapted to couple the coaxial illumination of the third and fourth observation pupil 8, 9 to the coaxial illumination 6 of the first observation pupil 4 and the main illumination 7 of the second observation pupil 5. The coupling can be implemented in the control subsystem 21 using a non-linear or linear coupling characteristic 22. The characteristic 22 can further be implemented by using a simple constant in the form of a target ratio.

A linear or non-linear coupling characteristic may be used to adapt intensity changes better to any intensity-dependent characteristic of perception in the observer's eyes. The coupling can be implemented mechanically, e.g. by mechanically transmitting a motion from one manipulator to another via gears. The coupling can also be implemented electrically by using analog electric components such as amplifiers, resistor networks and capacities to arrive at the desired dependency of the main illumination 7 from at least one of the coaxial illuminations 6, 10, 11. If the coupling is implemented digitally, a digital control may be used, wherein the coupling characteristic 22 may be, e.g. stored as a look-up table.

The coupling characteristic 22 may be stored in a memory subsystem 23, which may comprise mechanical, electric, analog and/or digital components. In its simplest form, the coupling characteristic 22 is just a target ratio of the main illumination 7 to at least one of the coaxial illuminations 6, 10 and/or 11 which is maintained by the control subsystem 21 if the intensity in one of the coaxial illumination 6, 10, 11 changes.

A change in the intensity may be effected by operation of a manipulator subsystem 24. Again, the manipulator subsystem 24 may comprise manually operable manipulators such as adjustment knobs or sliders, and/or electric elements such as adjustable resistors, gates or logical circuits in order to change the intensity of at least one, preferably each of the light sources 16. The manipulator subsystem 24 may also comprise software-implemented manipulators such as virtual sliders or adjustment knobs which are displayed on a computer screen for interaction with a user.

In FIG. 7, two manipulator elements 25 are shown just by way of example. One of the manipulator elements 25 can be activated to control the intensity of the light source 16 of the main illumination 7. The other manipulator element 25 serves to adjust commonly the intensity of all three light sources 16 for the coaxial illuminations 6, 10, 11.

A switch 26 may be provided as part of the manipulator subsystem 24 to activate a subset of the manipulator elements 25 and/or to switch the illumination and observation system 1 from a coupled state, in which the main illumination 7 is coupled to at least one of the coaxial illumination 6, 10 and 11, to a decoupled state, in which this coupling is released and the intensities of these illuminations can be adjusted independently. It is preferred that upon switching from a decoupled to the coupled state, the newly obtained ratio between the intensity of the illumination in one of the coaxial illuminations 6, 10, 11 is stored in the memory subsystem 23 as the new target ratio.

This allows for example that the surgeon adjusts the relative intensity of the main illumination 7 to the coaxial illumination 10, 11 to a ratio, which for him individually yields the best stereoscopic image. For this adjustment, the switching subsystem 26 is activated and the decoupled state is assumed. Once the surgeon has adapted the relative intensities of the coaxial and the main illumination 10, 11, 7 to his needs, he again activates the switching subsystem 26 in order to commit the new target ratio to the memory subsystem 23 and switch to the coupled state. From now on, any change of the intensity of the coaxial illuminations 6, 10, 11 automatically triggers a corresponding change in the intensity of the main illumination 7 to maintain the target ratio. This coupling and intensity change is controlled by the control subsystem 21.

Especially for maintenance purposes, it may be desirable that the illumination and observation subsystem 1 can be switched into a decoupled state, in which the intensities of all light sources 16 can be adjusted independently of each other. Once this adjustment is done and the decoupling is switched off to enter the coupled state, the relative intensities of all the light sources 16 may be committed to a storage subsystem.

Although the storage subsystem 23 and the switching subsystem 26 as well as the manipulator subsystem 24 are shown to be separate from the control subsystem 21, all these subsystems may be integrated into a single control unit 27, such as a computer or an ASIC.

REFERENCE NUMERALS

-   -   1 illumination and observation system     -   2 microscope     -   3 main objective lens     -   4 first observation pupil     -   5 second observation pupil     -   6 coaxial illumination     -   7 main illumination     -   8 third observation pupil     -   9 fourth observation pupil     -   10 coaxial illumination in third observation pupil     -   11 coaxial illumination in fourth observation pupil     -   12 optical axis     -   13 red reflex     -   14 beam splitter or deflecting optical element     -   15 beam splitter or other deflecting optical element     -   16 light source     -   17 LED     -   18 optical elements for coaxial illumination     -   19 optical elements for main illumination     -   20 illumination path     -   21 control subsystem     -   22 coupling characteristic     -   23 memory subsystem     -   24 manipulator subsystem     -   25 manipulator elements     -   26 switch     -   27 control unit 

What is claimed is:
 1. Illumination and observation system (1) for a microscope (2) for performing eye surgery on an observed eye, the system (1) comprising: a main objective lens (3) having a first observation pupil (4) and a second observation pupil (5) for the eyes of an observer; a coaxial illumination (6) in the first observation pupil (4), the coaxial illumination (6) being adapted to generate a red reflex (13) in the observed eye in operation; wherein a main illumination (7) is provided in the second observation pupil (5) having a larger field of illumination in an object plane of the microscope than the coaxial illumination (6), and wherein a control subsystem (21, 27) is provided which is adapted to automatically adjust an intensity of the main illumination (7) depending on a change in an intensity of the coaxial illumination (6), and wherein there is no overlap of the main illumination (7) with the first observation pupil (4) and there is no overlap of the coaxial illumination (6) with the second observation pupil (5).
 2. Illumination and observation system (1) according to claim 1, wherein the control subsystem (21, 27) is adapted to set a ratio of the intensity of the main illumination (7) to the intensity of the coaxial illumination (6) at a target ratio independent of a change in the intensity of the coaxial illumination (6).
 3. Illumination and observation system (1) according to claim 2, further comprising a memory subsystem (23, 27) adapted to store the target ratio.
 4. Illumination and observation system (1) according to claim 3, further comprising a manipulator subsystem (24, 27) adapted to interact with at least one of the control subsystems (21, 27) and/or the memory subsystem (23, 27), the manipulator subsystem (24, 27) further being adapted to change the target ratio upon a manual input from an observer.
 5. Illumination and observation system (1) according to claim 4, wherein the manipulator subsystem (24, 27) is adapted to change the intensity of at least one of the coaxial illumination (6) and the main illumination (7) upon operation.
 6. Illumination and observation system (1) according to claim 1, wherein the main illumination (7) overlaps an optical axis of the second observation pupil (5).
 7. Illumination and observation system (1) according to claim 1, wherein the main illumination (7) is coaxial within +/−5° to an optical axis (12) of the second observation pupil (5).
 8. Illumination and observation system (1) according to claim 1, further comprising a third observation pupil (8) and a fourth observation pupil (9), each of which is provided with a respective coaxial illumination (10, 11).
 9. Illumination and observation system (1) according to claim 8, wherein an intensity of the coaxial illumination (6) of the first observation pupil (4) is coupled to an intensity of the coaxial illumination (10, 11) of at least one of the third and fourth observation pupils (8, 9).
 10. Illumination and observation system (1) according to claim 8, further comprising a manipulator subsystem (24, 27) adapted to switch the illumination and observation system (1) from a coupled state, in which the intensity of the main illumination (7) is coupled to the intensity of the coaxial illumination (6, 10, 11) in at least one of the first, third and fourth observation pupil (4, 8, 9), to a decoupled state, in which the intensity of the coaxial illumination (6, 10, 11) in at least one of the first, third and fourth observation pupils (4, 8, 9) is decoupled from the intensity of the main illumination (7).
 11. Illumination and observation system (1) according to claim 8, wherein the field of illumination created by the main illumination (7) is between 2 and 5 times larger than the field of illumination created by any of the coaxial illuminations (6, 10, 11) in the first, third and fourth observation pupils (4, 8, 9).
 12. Illumination and observation system (1) according to claim 8, wherein the coaxial illumination (6, 10, 11) of at least one of the first, third and fourth observation pupils (4, 8, 9) and the main illumination (7) have separate light sources (17).
 13. Illumination and observation system (1) according to claim 12, wherein each of the coaxial illuminations (6, 10, 11) and the main illumination (7) overlaps at least 50% of the first, second, third and fourth observation pupils (4, 5, 8, 9).
 14. A microscope (2) for eye surgery, wherein the microscope comprises an illumination and observation system (1) according to claim
 1. 15. A microscopying method for illuminating an observed object, the method comprising: using coaxial illumination (6, 10, 11) to illuminate the observed object coaxially through first, third, and fourth observation pupils (4, 8, 9) of a main objective lens (3); providing a main illumination (7) to a second observation pupil (5) of the main objective lens (3) to illuminate the observed object with a larger field of illumination in an object plane than the coaxial illumination, wherein an intensity of the main illumination (7) is controlled to automatically follow an intensity of the coaxial illumination, wherein there is no overlap of the main illumination (7) with the first observation pupil (4) and there is no overlap of the coaxial illumination (6) with the second observation pupil (5).
 16. Illumination and observation system (1) for a microscope (2) for performing eye surgery on an observed eye, the system (1) comprising: a first observation pupil (4) and a second observation pupil (5) for the eyes of an observer; a coaxial illumination (6) in the first observation pupil (4), the coaxial illumination (6) being adapted to generate a red reflex (13) in the observed eye in operation; wherein a main illumination (7) is provided in the second observation pupil (5) having a larger field of illumination in an object plane of the microscope than the coaxial illumination (6), and wherein a control subsystem (21, 27) is provided which is adapted to automatically adjust an intensity of the main illumination (7) depending on a change in an intensity of the coaxial illumination (6), and wherein the control subsystem (21, 27) is adapted to set a ratio of the intensity of the main illumination (7) to the intensity of the coaxial illumination (6) at a target ratio independent of a change in the intensity of the coaxial illumination (6).
 17. Illumination and observation system (1) according to claim 16, further comprising a memory subsystem (23, 27) adapted to store the target ratio.
 18. Illumination and observation system (1) according to claim 17, further comprising a manipulator subsystem (24, 27) adapted to interact with at least one of the control subsystems (21, 27) and/or the memory subsystem (23, 27), the manipulator subsystem (24, 27) further being adapted to change the target ratio upon a manual input from an observer.
 19. Illumination and observation system (1) according to claim 18, wherein the manipulator subsystem (24, 27) is adapted to change the intensity of at least one of the coaxial illumination (6) and the main illumination (7) upon operation. 